Note: Descriptions are shown in the official language in which they were submitted.
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~ 1 70436
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PIPE COUPLING JOI2JT AND
: I~ETHOD AND APPARATUS FOR MAKING S~E
This invention relates to methods and apparatus for
joining lengths of non-threaded metal pipe. More particularly,
it relates to methods and apparatus for interference fit joining
of lengths of pipe to for~ a continuous conduit, and to the
joint formed by such methods and apparatus.
Various methods have heen used for joining lengths
of pipe to foxm a continuous conduit. Perhaps the most co~non
pipe joining method involves the joining of an externally
threaded pin end of one pipe section with an internally threaded
box end of another pipe section. The interconnection i5 generally
called a joint and in the case of threaded ends is called a
threaded joint.
~, While satisfactory for many purposes, threaded pipe
! joints are relativeIy expensive to prepare and considerable
time is required to form a junction therebetween. For example,
: at least one length of pipe must be rotated to join threaded
pipe, thereby rendering it difficult if not impossible to
join two relatively long lengths of pipe with conventional
i threaded ends.
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~l 20 Other joining methods, such as welding, are comrnonly
` used to join pipe. However, in many applications it is
¦ necessary to provide the entire inner surface of a conduit
with a protective liner. The internal surfaces are best
protected with a liner of polyvinyl chloride bonded to the
;~ 25 internal surface of the pipe as described in U.S. Patent
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1 ~7043G
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No. 3,758,361 to John J. Hunter. When the internal surface
of the conduit is protected by such a liner, means must be
- provided for joining the ends of the liners at the junction
of two pipe,lengths so that the liner is continuous and the
entire internal surface of the conduit formed is continuously
lined. Because of the heat required in welding pipe ends
together, welding cannot be commonly used to join lengths
of lined pipe since the liner will melt and separate from
the pipe walls when the pipe is welded.,
For forming conduits in which the pressure of the
fluid to be conducted through the pipe is relatively low,
various types of non-threaded joints have been devised~
Non-threaded joints are typically formed by enlarging the
internal diameter of one end of the pipe section to a
I 15 diameter slightly less than the external diameter of the
I pipe. The enlargement is usually formed by forcing a
¦ mandrel of the desired dimensions into one end of the pipe
1 and thereby eniarging or swelling the end of the pipe.
¦ The enlarged end is commonly referred to as a bell and the
1 20 end of the adjoining pipe which fits within the bell is
I commonly referred to as the pin end or spigot.
! Conventionally, the bell is formed by forcing a mandrel
¦ of desired shape into one ,end of the pipe to form a bell
! f enlarged dimensions with a flared end so that the pin
end may be~inserted into the flared portion and forced
into the remaining portion of the bell. Such joints are
commonly referred to as interference fit ~oints and are
commonly used in applications wherein the pressure of'the
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fluid passing through the conduit is relatively low, such
as, for example, in automobile exhaust pipes and the like.
Since the internal diameter of the bell is less than the
external diameter of the pin, the bell must be slightly
expanded radially as the pin is axially inserted therein,
The difference in diameters is conventionally known as
the interference and the friction between the walls
interference fitted together f,orms the 30int or coupli~g
force. Since the external diameter of the pin is greater
than the internal diameter of the box, the box is expanded
radially as tXe pin is inserted therein, Obviously, the
pin and box must have substantially non-tapered cylindrical
dimensions. Otherwise, the entire bell would be expanded
radially simultaneously rather than expanded progressively
as the pin is inserted axially therein, Therefore, as used
herein, the term "substantially parallel inner walls over a
"~ major portion of the axial length thereof" is used to define
a bell which has substantially cylindrical dimensions as
contrasted to tapered dimensions, Likewise, the term
"substantially axial parallel external walls" is used herein
to define a pin which has substantially cylindrical dimensions
as contrasted to tapered dimensions,
One of the main advantages of interference fit joints
is that they may be formed relatively quickly and inexpensively
and neithe~ pipe section need be rotated to form the junction.
Furthermore, since excessive-heat is not requixed to form an
interference fit joint, plast,ic lined joints may be formed with
appropriately designed ends on the plastic liner, Among the
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disadvanta~es of conventional interference fit joints is that
the joint is usually incapable of withstanding high pressures
and will either leak or separate if the conauit is subjected to
high internal pressures.
U.S. Patent NoO 3,208,136 to Joslin di sc lose s ~
modification of the conventional interference fit joint. In
the method disclosed in U.S. Patent No. 3,208,136 an annular
groove is formed in the pin ena of the pipe. The pin end is
telescoped within the bell with such force that the pin end
-buckles in the region of the annular groove when the pin end
strikes the shoulder of the bell. As the pin end buckles the
portion of the inner pipe adjacent the groove is forced outwardly `-
aga`inst the inside wall of the bell to aeform the bell and form
` corresponding grooves in the bell. In this manner intexlocking
' grooves are formed between the pin end'and the bell end which,
when properly formed, form a leak-proof joint of substantial
rigidity which is capable of withstanding high internal pressures.
One of the major disadvantages, however~ of the huckle joint
formea according to the Joslin patent is that the method may only
be satisfactorily used with relatively thin walled pipe or soft
pipe such as aluminum. 'When thicker walled pipe is used, the
buckle fails to form corresponding grooves in the bell ana the
joint formed thereby is not satisfactorily mechanically coupled.
Therefore, when subjected to high internal pressure, the joint
tends to separate.
In accordance with the present invention, methods and
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apparatus are provided'for'-forming a rigid` joint between either '
t'hick or thin walled non-threaded steel pipe. The joints are
formed by forming a bell in one pipe end as in conventional
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interference fit join;ng method~. The p;n end is then forced ;nto the bell
and thereafter the end of the bell ;s radially compressed suff;c;ently to
form a groove ;n the p;n end so that the end of the bell f;ts within the
i groove fonmed. In this manner the pipe joints are mechanically locked. The
compressed or crimped end may be formed a~ter the inter~erence joint ;s
formed or contemporaneously therewith and the junct;on formed thereby is
capable of handling extremely high internal pressures w;thout separation or
leakage. Furthermore, s;nce the internal surfaces of the jo;ned pipe are
substantially unaffected by the join;ng method, continuously l;ned p;pe
condu;ts can be read;ly formed.
The ;nvent;on also prov;des an apparatus for joining pipe
sections comprising means for holding a second pipe section in axial
. alignment with a first pipe section, means for holding said first pipe
section in axial alignment with said second pipe section and simultaneously
axially telescop;ng the end of said first pipe section within the end of
" said second p;pe section; and means for deforming a portion of said second
pipe section radially ;nwardly to form an annular groove in sa;d first
pipe sect;on and fit said portion of said second pipe section within said
annular g~oove.
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Other features and advantages of the invention will become
more readily understood when taken in conjunction with the appended claims
and attached drawings, in which:
Figure 1 is a sectional view of the box end and pin end of
. . 5 lined pipe immediately pr;or to jo1ning therèof in accordance with the
invention;
Figure Z is a sectional view of the junct;on formed between
the pipe ends illustrated in Figure 1 in accordance with the invention;
Figure 3 ;s a perspective view of apparatus for forming a
pipe joint as illustrated in Figure 2;
Figure 4 is a sectional view of the crimping head illustrated
in Figure 3;
Figure 5 is a top plan view of the bottom yoke of the crimping
head; and
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8 3 ~`~43~
FIGURE 6 is a sectional view of an end sizing
` apparatus for preparing the pin end of pipe section to be
formed in accordance with the invention.
Since one of the major aavantages of the pipe
joining method of the invention is the ability to form
junctions between lined pipe joints and therefore form a
continuously lined conduit, the invention will be described
with particular reference to joining lined pipe. It should
be understood, however, that the invention is not so limitea.
The principles of the invention apply equally to unlined
` pipe and lined pipe.
In conventional pipe joining methods, a pipe
section of finite length is joined with another pipe section
of finite length and the process repeated to form a continuous
conduit~ Conventionally, one end of the pipe is formed -to
receive the end of the adjacent pipe section. Therefore,
each pipe section is ordinarily prepared to ha~e a bell or
; box on one end and a pin end on the opposite end. Ordinarily
only one end of the pipe is enlarged to form a bell. The
opposite end of the pipe is usually used as ~he pin end in
its unenlarged or unchanged state. If desired, however, the
pin end may have reduced dimensions. The ends of adjacent
pipe sections to be joined in accordance with the preferred
I methoa on the invention are illustrated in FIGURE 1.
¦ 25 The pipe sections 10 and 11 illustrated in FIGURE 1
¦ may be any conventional metal pipe. One end of pipe 10 is
enlarged to form a bell 12. The enlarged bell 12 is formed
by conventional means such as forcing a mandrel into the end
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of the pipe to swell or enlarge the end of p;pe 10 to the des~red
dimens;ons. Convent;onally, the bell 12 will be compr~sed of three
sections; an enlarged sectlon 12a in which the internal walls of
- . the bell are substant;ally parallel thus having a substant1ally
uniform diameter, a neck or shoulder port;on 12b (the sect;on of p~pe
jo;ning the enlarged section 12a with the remainder of the pipe 10)~
and a flared portion 12c at the mouth of the bell. It will be readily
understood that the neck 12b simply interconnects the bell with the
pipe section and thus forms a shoulder 13 at the base o~ the bell.
Since the internal diameter of the bell 12-is ordinarily slightly less
than the external diameter of the pin end of section 11, a flared
portion 12c is formed at the end of the bell simply to accommodate
ease of inserting the pin end 11 within the bell 12. The flared
portion 12c, therefore, is not essential. In the preferred embodiment
of the invention the sides or walls of the bell 12 are substantially
parallel and the pin end of the pipe has the same dimensions as the
remainder of the p;pe body.
The pipe sections illustrated ;n Figure 1 may be
jo;ned in conventional manner with an interference fit joint by
telescoping the pin end of pipe 11 within the bell 12. Since the
internal diameter of the bell 12 is slightly less than the
~ external d;ameter of the pin end of pipe 11, substantial force ;
~ is required to telescope the pin within the bell. Thus the bell
may be slightly further radially enlarged upon insertion of the pin
end axially therein. Because of frictional forces between the
engaged side~ of the bell and the p;n end, a relatively good seal
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1 370~36
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is formed between the bell and pin, thus forming a sealed
conduit. This method of forming an interference fit joint
: is conventional and, with the exception of the end crimping,
seallng and internal liner. (to be.described hereinafter), is
known in the art.
In accordance with the invention, the end of the
bell 12 (substantially corresponding with the flared portion
12c) is radially compressed after the junction is formed or
simultaneously therewith. The end is compressed or crimped
sufficiently to form a groove 14 in the pipe 11 after the l
pin end of pipe 11 has been inserted within the bell as
illustrated in FIGURE 2. By crimpin.g the flared end 12c
into the pipe 11, a mechanical lock is formed, thereby
interlocking the pipe sections together. Joints formed as
described are found in most cases to have greater mechanical
strength than the remainder of the pipe body, and when conduits
formed using the joint described are subjected to high internal
pressures, the pipe wall will rupture before the joint will
. break.
~0 The joint ~escribed hereinabove may be formed
using any substantially rigid conduit having malleable.
characteristics, such as steel pipe, aluminum pipe or
pipe made of other metal alloys. Furthermore, the wall
thickness of the pipe is not critical since the end crimping
~5 can be performed on thick walled steel pipe as well as thin
walled so~ter conduit.
` The axial length of the bell, which determines
the axial length of interference fit between the two pipe
~ ~ ~04~6
sections, may vary according to the characteristics of the
pipe and the use for which the conduit is intended. As a
typical example using steel pipe of 3.5 inches in diameter with
a wall thickness of 00237 inch, the bell is about 5 3/4 inches
long. The internal diame~er of the bell end is enlarged
so that the internal diameter of the bell is approximately
0.040 inch less than the external diameter of the pin end.
This difference in diameters is commonly referred to as
the interference fito As is commonly known, the amount of
interference fit may vary depending on wall thickness of
the pipe, the material of the pipe, the amount of pressure
to be used on the fluid flowing through the pipe, and the
length of the bell. An interference fit of 0.030 to 0.050
inch has been found satisfactory for common steel and
aluminum pipe. It has been discovered, however, that the
external diameter of some pipe, particularly thick walled
steel pipe, may vary substantially from manufacturer to
manufacturer. Furthermore, the pipe may not be perfectly
circular in cross-section. Accor~ingly, when a standard
sized mandrel is used to form the bell, the external
diameter of the pin end may be substantially larger than
the internal diameter of the bell. Therefore, the
interference may be larger than desired. When the
' interferen`ce is larger than about 0.060 inch, severe
¦ ~5 galling may occur upon insertion of the pin end within
the bell. To prevent galling and assure uniform mating
of the pin end within the bell, it is often desirable to
` size the pin end prior to completion of the joint.
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Sizing may be readily accomplished by forcing a sleeve
or ring having internal dimensions of the desired
external dimensions of the pin over the pin end of the
pipe, thereby slightly compressing the pin end of the pipe
5 to approximately the desired interference fit size.
Sizing of the pin end assures uniform interference
fit between the pin and the bell and also assures that mill
scale and the like for~ed on the external surface of the
pipe will be removed prior to completion of the joint. This
assures a more uniform joint and a better seal between the
external surface of the pin and the internal suxface of the
bell. More importantly, sizing of the pin end prevents
galling o~ the bell during the insertion operation, therefore
assuring a uniformly sealed joint.
Apparatus ~or sizing the pin end in accordance
with the invention is illustrated in section in ~IGURE 6.
The sizing apparatus comprises a cylindrical sleeve 90
with a cylindrical cavity 91 having internal dimensions
which correspond to the desired external dimensions of
the pin end. The sleeve 90 has a pedestal shaft 92
extending from the closed base thereof. The pedestai 92
is placed in à pipe press and the end of the pipe to be
sized is placed co-axially aligned with the open end of
the sleeve 90. The open end o the sleeve is internally
enlarged to form an annular cavity 94 which is greater
than the external dimensions of the pipe. An annular
shoulder 93 is thus formed within the cavity 91. A
hardened steel ring 95 having tapered inner surface 96
1 ~ 7~3~
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- is held adjacent the shoulder 93 by retainer ring 97.
The internal surface of ring 95 tapers from the diameter
of annular cavity 94 to the diameter of cavity 91.
The pin end of the pipe section is forced,into
the cavity 91. Any portio'n of the pin end larger than
the internal diameter of the ring 95 strikes the tapered
surface 96 and thus is compressed to the desired dimensions
by being forced through the sizing ring 95. In this manner
oval or eccentric shaped plpe is made circular in cross
section and any pipe with oversize external dimensions is
sized to standard dimensions. Similarly, the external
dimensions of the pin end may be reduced to any desired
- dimensions. In the embodiment illustrated, the sides of
cavity 91 are parallel except for a small tapered region 98
, 15 at the base thereof. The tapered region 98 forms a slight
taper on the end of the pipe to insure that the end of the
,` pin does not scrape the walls of the bell as the joint is formed.
~hen sizing the ends of pipe sections it is
'desirable that the pipe be lubricated. Any lubrication,
such as grease or the like, may be used to prevent the pipe
from welding to the sizing sleeve. Accordingly, the sleeve
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;~ ' may then ke withdrawn and the pipe is ready for use.
Sizing the pipe as described above not only assures
uniform intexference fit between the bell and pin, but also
cleans the pin end so that maximum interference en~agement
will occur when the joint is formed and any pipe sealant to
be used will firmly adhere to the pipe.
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Compressing the end of the bell to form the
crimped interlock as described above may be performed by
various methods. Any apparatus which deforms a portion of
the bell into a corresponding groove in the pin end formed
by compressing the bell may be used. In the preferred
embodiment uniform radial compression is accomplished by
partially forcing a crimping collar axially over the end
of the bell after the interference fit joint is formed.
The collar has an internal diameter which is divergent
from a diameter of slightly more than the external diameter
of the pipe 11 to an internal diameter greater than the
external diameter of the flared portion 12c of the bell.
The flared collar is placed over the pipe 11 with its
internal diameter expanding in the direction of the pin end
of the pipe. After the interference fit joint has been
formed, the collar is moved axially over the pipe 11 to
engage the flared end 12c of the bell. Since the collar is
flared and completely surrounds the pipe 11, the end 12c of
the bell is uniformly radially compressed and forced into
the pipe to form groove 14. The end 12c is thus permanently
: deformed and fitted into the groove 14 to form an intexlocking
; joint as illustrated in FIGURE 2.
Fully lined conduit may be formed as illustxat~d in
.
FIGURES 1 and 2 using the pipe joining method of the invention.
, 25 To form a ~ully lined joint a liner is positioned within the
~` pipe sections 10 and 11. The iiner may be any suitable
conventional liner but is preferably a polyvinylchloride
liner bonded to ~he internal surface of the pipe 10 and 11 as
1 3 7~36
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- described in U.S. Patent No. 3,758,361, The polyvinylchloride
(PVC) linex is bonded to the internal surface of the pipe 10
i after the bell has been formed therein. The end 16 of PVC
liner 15 is expanded to conform to the internal dimensions of
the flared neck portion 12b of the pipe. The end 16 extends
into the flared neck 12b but not past shoulder 13 as illustrated
- in FIGURE 1. The e~d 17 of liner 15 extends past the open end
of the pin end of pipe 11. The end 17 extending from the pin
end of pipe 11 is slightly expanded so that the external
di~ension thereof is less than the external dimension of pin
end 11 but greater than the internal dimension of pin end 11
as illustrated in FIGURE 1. In this manner the end portion 17
of liner lS extending past the end of pin end 11 will fit within
the end 16 of liner 15 in the throat of the bell when the pin
end of pipe 11 meets the shoulder 13 in the bell.
To form a seal between the overlapped portions of
the plastic liner the external surface of end portion 17
extending from pin end 11 is coated with a suitable adhesive,
~" solvent, cement or the like immediately prior to insertion of
the pin end within the bell.
In the preferred embodiment of the invention a
conventional PVC joint cement is applied to the external
surface of the end portion 17 in sufficient amounts to fully
;` cover the external surface of the end portion 17 extending
fxom the pin end so that the end portion 17 will be unifoxmly
bonded to the internal surface o~ the end portion 16 within
the throat of the bell when the joint is completed. Accordingly,
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a continuous liner i5 formed on the internal surface of the
joint as well as the internal surface of the pipes when the
joint is completed.
In forming conventional interference fit joints a
lubricating agent is sometimes applied to the pin end of the
pipe to aid in inserting the pin end within the bell. When
a conventional lubricating agent is used, care must be taken
to avoid mixing the lubricating agent with the PVC cement or
other bonding agent used unless the cement is also to be used
as a lubricating agentO Where a lubricating agent is used
which will interfere with the formation of a bond between the
ends of the PVC liner, care should be taken to avoid mixing
of the lu~ricating agent with the bonding agent.
In the preferred embodiment of the present invention
an epoxy resin is used as a lubricating agent and also to aid
in forming a metal-to-metal bond between the bell and pin ends
of the pipe. Any suitable conventional bonding agent may be
used. A two part epoxy resin bonding agent for forming
metal-to-metal seals has been ~ound particularly suitabl~.
The preferred epoxy resin is a metal bonding agent sold
under the name Steel Seam by Cooks Paint & Varnish Company
` of Kansas City, Missouri. This bonding agent is a two
- part epoxy agent comprising a curing agent (sold under the
trade designation 920L927) which is mixed with a base
(sold under the trade desi~nation 920W979). The curing
agent and base are mixea immediately prior to use and
applied to the external surface of the pin end of the pipe
immediately prior to insertion of the pin within the bell.
Care should be taken to avoid mixing the metal to-metal
~ ~ 7~36
bonding a~ent with the PVC cement. The lubricating/bonding
agent is applied only to the pin end~ If the lubricating
agent is placed within the bell prior to insertion of the
pin end, the PVC cement may be mixed with the lubricating
S agent and/or the lubricating agent may become trapped
between the end of the pin and the shoulderA The trapped
fluid will be forced out between the overlapping ends of
the plastic liners as the pin end approaches the shoulder
13. Therefore undesirable contamination of the PVC bonding
agent will occur. Furthermore, the overlapped portions of
-~ the PVC liner will be separated and not seal properly.
It has been found, however, that the particular
two part epoxy described above may be used for both bonding
.~ the PVC liners as well as the metal joint. While the
plastic-to-plastic seal achieved is not of the quality
achieved with PVC cement, it has been found suitable in most
~; applications. Therefore a single application of this epoxy
may serve as the lubricating agent, the metal-to-metal bonding
agent, and the plastic-to-plastic bonding agent and the
problems of contamination totally eliminated.
Apparatus for forming a pipe joint in accordance
with the invention is illustrated in FIGURE 3. In the
preferred embodiment the apparatus comprises a pair of press
heads 20 and 21 adapted ~or reciprocal movement with respect
to each other and powered by suitable hydraulics. In the
embodiment illustrated the apparatus comprises a stationary
head 20 mounted on suitable supporting framework 22. The
stationary heaa 20 comprises an elongated yoke with a pair
1 17~36
of hydraulic cylinders 23 and 24 rigidly affixed at the
opposite ends of one side thereoX. Hydraulic cylinders 23
and 24 are mounted to ex~end in a plane horizontal to the
yoke and are parallelO A slip receiving bowl is centrally
formed in the head 20 with its axis transverse to the yoke ;
and parallel with the central axes of cylinders 23 and 24. '¦
A pair of doors 26 are mounted on head 20 by means of hinges
` 27. Each door 26 carries a pair of slip sections 28 which
cooperate with slip section 29 in the bowl in the yoke.
Upper slip section 28 and lower slip section 29 are
removably mounted in the bowls by conventional means such ;
as dovetail keys 39 and form corresponding conventional
slips to engage a pipe section positioned therein parallel
with the cylinders 23 and 24. Slip sections 28 and 29 are
conventional parallel slips removably mounted within the bowls
` and are adapted to be interchangeable so that siips of various
internal diameters may be used as desired to accommodate various
pipe sizes.
Door closing hydraulic cylinders 31 are pivotally
mounted on the yoke ~as illustrated in phantom in FIGURE 3) with
the piston rods 32 connected to doors 26. Door cylinders 31 are
double ac~ing cylinders, thus may be used to open and close the
doors 26 as well as apply pressure to the slips to grip the pipe.
As noted above, hydraulic cylinders 23 and 24 are
rigidly attached to head 20 by means of mounting shafts 35 and
36 extending axially from the base of the cylinders through the
head 20 and secured by nuts 34. Similarly, the ends of piston
rods 37 and 38 extending from cylinders 23 and 24, respectively,
are rigidly attached to the ends of traveling head 21. Cylinders
I ~ 7 ~3 J
23 and 24 are double acting cylinders of the same siæe and are
~ simultaneously activatea. Accordingly, traveling head 21 is
-~ not attached to frame 22 but may ride thereon if desired. ~nall other respects traveling head 21 is essentially iden~ical to
stationary head 20. By rigidly affixing the cylinders 23 and 24
to stationary head 20 and the ends of piston rods 37 and 38 to
` the traveling head 21, the central axis of the slips in the
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;~ stationary head is permanently aligned with the central axis of
the slips in traveling head 210 Therefore, misalignment of the
pipe sections is avoided. Unless the pipe sections 10 and 11
are substantially axially aligned and maintained in aiignment
`~" during the joining operation, the pin end may unduly scrape one
side of the bell and cause galling when the joint is formed.
Therefore, it is desirable that the traveling head 21 be
securely and rigidly affixed to and supported by the piston
rods 37 and 38. Additional pipe supporting means ~not shown)
may be positioned at either end of the apparatus to assure
proper alignment of the pipe sections during assembly.
In the apparatus illustrated in FIGURE 3, means for
radially compressing the mouth of the bell is illustrated at
` 50. The radial compression head 50, generally referred to
` herein as the crimping head, is shown in detail in FIGURES
4 and 5. In the preferred embodiment the crimping head 50
comprises a pair of vertically opposed yokes 51 and 52
positioned between the stat:ionary head 20 and the traveling
head 21. The bottom yoke 52 has a semi-cixcular bowl 53
centrally disposed in the top surface thereof. Top yoke 51
has a corresponding semi-cylindrical bbwl 54 in the~bottom
1 ~7~3~ '
surface thereof. Bowls 53 and 5g form a cylinder with its
central axis aligned with the central axis of the slips in
the stationary head 20 and the traveling head 21 and carry
mating semi-circular members which form a crimping collar.
The lower yoke 52 rides freely within frame 22 as
illustrated in FIGURE 4. Crimping cylinders 55 and 56 are
mounted on the lower surface of bottom yoke 52.
The piston rods 57 and 58 extending from cylinders
55 and 56, respectively, pass vertically through vertical
holes 59 and 60 in the lower yoke 52. Rods 57 and 58 also
extend vertically through holes 61 and 62, respectively, in
the upper yoke 51. As shown in FIGVRE 4~ the holes 61 and
62 in the upper yoke 51 are of smaller diameter than holes
59 and 60 in the lower yoke and the portion of rods 61 and
62 extending through the upper yoke 51 are of reduced diameter
to correspond to the size of the holes 61 and 62 in thè upper
yoke. Accordingly, the bottom surface of upper yoke 51 rides
on shoulders 63 and 64 of rods 57 and 58, respectively, and
the upper yoke 51 is securely fastened to the rods by suitable
means such as nuts 65 and 66. It will thus be observed that
since the cylinders 55 and 56 are attached to the lower yoke
52 and the piston rods 57 and 58 are attached to the upper
yoke 51, simultaneously sUpplying fluid to the upper end of
cylinders 55 and 56 draws yokes 51 and 52 together like a
guillotine; Similarly, simultaneously supplying hydraulic
fluid to the lower ends of cylinders 55 and 56 opens the
yokes 51 and 52.
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As illustrated in FIGURE 4, hydraulic cylinders 55
,~ and 56 extend laterally from the ends of yoke 52. Bottom
yoke 52 rides within the frame members 22 and extends below
` the frame members 22 a distance of about an inch or-more~
S Accordinglyt the entire crimping head assembly may move
, vertically within the framework 22 the distance between the
frame 22 and the cylinders 55 and 56. In this manner the
crimping head 50 floats freely within the frame and when
the head is open (as illustrated in FIGURE 4) the lower
yoke 52 moves down from the central axis of pipe extending
th,rough the apparatus, thereby disengaging both the upper
, yoke and the lower yok~ from the pipe. Accordingly, pipe
- may be drawn hori~ontally through the apparatus without
engaging either the upper or the lower yoke and the apparatus
may be operated to join pipe without interference by the
crimping head.
The preferred embodiment of the crimping collar is
illustrated in detail in the top plan view of lower yoke 51
illustrated in FIGURE 5.
As illustrated in FIGURE 5 the semi-cylindrical bowl
53 is of stepped or graduated diameter. Therefore the bowl has
a larger diamet`er portion 53a on one side and a smaller diameter
53b on the opposite side forming a shoulder 53c within the yoke
52.
The diameter'of the larger bowl 53a is larger than
the diameter o~ the mouth of the bell on the pipe to be joined.
` ' The smaller diameter 63b must be at least-as large as the
diameter of the body of the pipe 11 adjacent the pin end.
4 3 6
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A crimping ring is formed by a pair of mating
semi-circular members, one in the upper yo~e and one in the
lower yoke 52. The semi-circular members 67 fit within the
larger bowl 53 as illustrated in FIGURE 5. The back of the
crimping ring 67 abuts shoulder 53c and the ring is held in
place by a retaining ring 68. The internal diameter of the
crimping ring 67 is tapered from a diameter slightly larger
than the diameter of the mouth of the bell to a diameter
slightly larger than the aiameter of the body of the pipe 11
adjacent the pin end. As illustrated in FIGURE 4, the smaller
diameter portion of the crimping ring 67 abuts shoulder 53c.
` An identical matching crimping ring is mounted
within bowl 54 in the upper yoke 51. It wlll thus ~e observed
that when the crimping head is closed the semi-circular members
within the bowls form a tapered collar of divergent diameter
diverging from a diameter slightly larger than the body of the
pipe 11 to a diameter larger than the largest portion of the
bell.
Operation of the apparatus of FIGURES 3, 4 and 5 to
produce the joint of the invention is apparent from the
drawings. A first pipe section is positioned within the
stationary head 20 and the slip doors 26 closed, thus gripping
the body of pipe 10 relatively close to the neck 12b o~ bell 12.
i A section of pipe 11 to be joined thereto is positioned within
the traveling head 21 and the slip doors closed to grip the
pipe 11 in the slips of the traveling head. Crimp head 50 is
positioned adjacent the traveling head 21 and maintained in the
open condition. Thus, the pin end of pipe 11 extends through
the open crimp head.
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3 &
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Cylinders 23 and 24 are activated to draw traveliny
head 21 toward stationary head 20. Since the pipe sections are
axially aligned the pin end o~ pipe 11 is telescopically forced
within the bell 12 progressively expanding the bell radially as
the end of the pin moves axially through the bell until the pin
end strikes shoulder 13. At this point the slips on the
traveling head are released and crimping head 50 is simultaneously
closed. When the slips in the. travelin~ head are released,
traveling head 21 moves axially over pipe 11 and continues to
travel toward the bell, thus driving the crimping head over the
bell. When the end of the bell strikes the crimping collar 67
within crimping head 50, the flared portion 12c of the bell is
uniformly radially compressed. As the crimping head 50
continues over the end of the bell, the flared portion 12c is
radially compressed inwardly until a groove 14 is formed in the
pin end by inward radial compression of the end portion 12c.
Since the crimping head 50 is free floating within
the frame 22, only the crimping ring 67 contacts the bell.
Thereby the crimping head is free to move to be axially
centered over the bell and uniformly compresses the mouth of
the bell from 360.
After the end has been crimped to the extent
desired, the cylinders 23 and 24 are reversed and the traveling
head 21 returned to the *irst position. Cximping head 50 is
then opened. When the head is opened the lower yoke 52 drops
away from the pipe and the upper yoke 51 is raised away from
the pipe so that the completed joint may be drawn through the
. .
apparatus. The slips on the stationary head are then opened
and the completed joint drawn through the apparatus.
: '
~ 1 7`~3~
Alternatively, the apparatus may be moved;to the ne~t pipe
joining position by drawing the apparatus over the pipe
If desired, the crimping head 50 can be closed
before completion of the interference fit joint. When the
crimping head is closed before the joint is formed, the
crimping head 50 travels with the traveling head 21 and slides
over pipe 11 until the bell is contacted by the crimping ring
67. The flared portion 12c of the bell is then automatically
and simultaneously crimped at the end of the insertion stroke.
To operate the crimping head in this manner, the stroke of the
traveling head must be predetermined so that the crimping ring
67 is in the proper posi~ion to form the crimp at the end of
the insertion stroke.
In the operation described hereinabove, the crimp is
formed by axially drawing the crimp head 50 over the bell while
the crimping ring is in a closed position. If desired, the end
of the bell may be crimped with the head illustrated by
positioning the crimping ring 67 over the mouth of the bell and
then closing the crimping head. The crimp is thus formed by the
opposing vertical movement of the yokes 51 and 52 while` the
crimping head is not moving in the axial direction. When operated
in this manner the radial compression force is applied primarili
to the top and bottom of the mouth (by the opposing action of the
yokes 51 and 52) rather than uniformly from 360 as occurs when
the ring 6i is drawn over the mouth of the bell. However, this
mode of operation may be used to crimp interference fit joints
previously formed or formed by other means or apparatus.
3 ~ 7~43G
When the crimping head 50 is moved axially as described
above the apparatus uniformly radially compresses the mouth 12c
of the bell into the pin end of pipe 11 as illustrated in FIGURE 2
to form a groove 14 with the entire circumference of the mouth 12c
S nested in the groove~ In this manner the pipe sections are
mechanically locked together and cannot be pulled apart without
deforming mouth 12c.
'- Best results are obtained when the mouth 12c of the
bell is radially compressed, by forcing ,tapered ring 67 axially
over the end thereof at the end of the insertion stroke as
described her inabove, thereby forming a crimp for the full
360 around the mouth and forming a full 360 groove 14 in the
pin end 11. The head 50 illustrated best performs this function
since it is free floating within the frame 20 and allows the
crimping ring 67 to automatically center around the axis of
the pipe. If desired, however, a crimping ring may be mounted
` on either the traveling head or the stationary head as desired.
However, the crimping ring should be driven by the head which
carries the pin end of the pipe so that axial pressure is
applied against the bell while the pipe, section carrying the
bell is held by the other head. Obviously, if the bel~ end of
` the pipe is not firmly held when the crimping head is driven
. . .
'` thereover, the crimping head may drive the bell o~f of the
' pin rather than crimp the mouth of the bell.
~ince the crimp head 50 illust,r,ated is free floating,
it may be reversea to allow either the traveling head or the
stationary head to hold the bell end during the assembly and
crimping operation. Alternatively, crimping rings may be
: I ~ 7043~
; ,
- attached to the inner faces of both the traveling head and
the stationary head and thus permit operation in alternative 1¦
directions.
While the invention has keen particularly described '
with reference to forming an enlarged bell in one end of a pipe ¦
section and inserting the pin end of an adjoining pipe section
within the bell, it will be readily apparent that the principles
of the invention may be used ~o join pipe ends of equal diameter
by bridging the joint with an elongated collar of larger external
diameter. In this method of operation the one pipe section is
gripped by either the stationary head or traveling head as ~'
described above and an elongated collar of larger external
diameter (having an internal diameter approximately 0.030 to
about 0~060 inch smaller than the external diameter of the pipe)
held by the other head. The collar is driven onto thé pipe end
and the mouth of the collar crimped as described hereinabove.
The end of the collar to which the pipe is attached is then
held in one of the press heads and the end of another pipe
forced within the opposite end of the collar and crimped.
In this manner the ends of the pipe need not be treated (except
for sizing) and the elongated collar performs the function of
a bell on both pipe sections.
In the embodiment illustrated, the mouth of the kell is
radially compressed to form a groove in the pin end of the pipe
for a fu11`360. It will be readily recognized, however, that a
full 360~ crimp is not necessarily required. Any portion of the
bell`may be crimped to`interlock the pipe sections without
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4 3 ~
departing from the principles o~ the invention. When less than
a full 360 crimp is used, however, the degree of mechanical
interlock will be proportionately reduced.
While the invention has been particularly described
with reference to crimping the mouth of the bell by forcing a
crimping ring thereover, it will be readily appreciated that
other means may be used for applying radial compression to the
mouth or other portion of the bell~ For example, a
circumferentially rotating inwardly compressing roller may be
used to roll the mouth of the bell into the pin end to
accomplish similar results. However, rolling the mouth of
the bell to form the crimp does not apply uniform radial
compression to the mouth and thus may not form as uniform a
crimping and sealing operation. However, use of a circumferential
radial compressing roller permits deformation of the bell at
locations other than the mouth thereof. For example, the
circumferential radial roller may be used to form one or more
.~ .
annular grooves or sections of annular grooves at various
locations along the length of the bell to form similar
mechanical inter~ocks.
As described above, the interference fit joint
formed in accordance with the in~ention forms a uniform seal
between the pin and bell as the pin is inserted within the
bell and expands-;the bell. As indicated above, in the preferred
~5 embodiment of the present invention a metal-to-metal epoxy resin
is used as a lubricant to prevent welding or galling of the parts
and to fill any scratches formed during insertion. The epoxy
resin fills any scratc~es formed and forms a complete
i 3 7~36
metal-to-metal bond between the mating pipe ends, thus assuring
a complete gas-tight seal while aiding in holdlng the joint
together.
Apparatus as described herein may be used to join
S malleable pipe of any size and wall thickness, depending only
upon the size and hydraulic capabilities of the apparatus designed.
It should be noted that the apparatus is of extremely simple
design and may be operàted either in the horizontal position
~as illustrated) or in the vertical position. Where required,
; 10 the apparatus may even be inverted and lowered into a trench
to make repairs.
For repetitive joining of pipe sections to form a
continuous conduit, the apparatus may be suspended from any
convenient carrier by framework 22 and carried to each pipe
joining station while the completed conduit is drawn through
.
the open slips.
It is to be understood that although the invention
has been described with particular references to specific
embodimènts thereof, the forms of the invention shown and
described in detail are to be taken as preferred embodiments
of same, and that variolls changes and modifications may be
resorted to without departing from the spirit and scope of
the invention as de~ined by the appended claims.
